1. Field of the Invention
The present invention relates to an in-finder display device suitable for displaying image-capturing information in a finder of, for example, a single-lens reflex camera.
2. Description of the Related Art
A so-called superimposed display function, in which image-capturing information is superimposed on a subject image in a finder of a single-lens reflex camera, is conventionally known. An example of a display device with such a function is disclosed in Japanese Patent Laid-Open No. 8-43913. In this display device, a plurality of focus-detection points in a finder screen are displayed in superimposed display mode, based on the structure in which a plurality of light-emitting elements correspond to respective reflecting surfaces of a deflecting part.
FIG. 9 shows the structure of the in-finder display device disclosed in Japanese Patent Laid-Open No. 8-43913.
A quick-return mirror 91 guides light from an image-capturing optical system (not shown) to a finder optical system. Light from a subject is reflected off the quick-return mirror 91 and forms an image on a focusing plate 92. The subject image formed on the focusing plate 92 is guided to the photographer's eye through an optical member 93 for superimposed display, a pentaprism 94 for inverting the subject image on the focusing plate 92 to form an erect image, and an eyepiece 95. Light from a light-emitting diode (LED) 96, which is provided for superimposed display, is guided through an illumination optical system 97 and the pentaprism 94 to the optical member 93. The optical member 93 is, as shown in FIG. 11, provided with prisms 111 on a surface adjacent to the focusing plate 92. A prism facet 111a and a prism facet 111b of each prism 111 reflect and allow light to pass through the illumination optical system 97 and the pentaprism 94 to reach the photographer's eye.
FIG. 10 is a perspective view showing the above-described in-finder display device (FIG. 9) viewed from obliquely above. LEDs 103a to 103e correspond to respective focus-detecting frames 121a to 121e within the finder field of view shown in FIG. 12. The LEDs 103a to 103e are turned on to illuminate the focus-detecting frames 121a to 121e, respectively. An illumination optical system 102 in FIG. 10 corresponds to the illumination optical system 97 in FIG. 9. The illumination optical system 102 has a powered surface (curved surface) facing a pentaprism 101. The powered surface is divided into three areas, that is, an area corresponding to the focus-detecting frames 121a and 121b, an area corresponding to the focus-detecting frame 121c, and an area corresponding to the focus-detecting frames 121d and 121e. The three areas guide light from the LEDs 103a to 103e, along the length of the finder field of view shown in FIG. 12, to the photographer's eye.
According to the structure described above, a plurality of focus-detection points arranged in and around the perimeter of the screen can be displayed in superimposed display mode.
However, the structure disclosed in Japanese Patent Laid-Open No. 8-43913 poses a problem in that an increase in the number of focus-detection points to be displayed in superimposed display mode leads to an increase in the size of the camera and increased costs, because additional illumination optical systems for guiding light from the light source to the photographer's eye, or additional powered surfaces of the illumination optical system are required.